Cardiac pacemakers, and other implantable stimulation devices such as cardioverters and defibrillators, are typically hermetically sealed within a housing or casing (sometimes also referred to as a “can”) to isolate the electronic circuits contained within the device from the body environment. Such devices require that electrical signals be reliably passed between the hermetically sealed circuitry and external connectors without compromising the hermeticity of the device. Depending on the configuration of the implantable device there may be multiple electrical paths required between the device and its external connectors for delivering, for example, multi-chamber or multi-site stimulation and shock therapy, and for receiving sensed cardiac signals. These paths should be electrically and mechanically integrated with the device to provide a safe, long-term lead retention assembly that does not compromise the hermetic package.
Typically, a hermetic housing feedthrough electrically couples the electronic circuits contained within the device housing to the lead retention assembly. The feedthrough may extend through the wall of the hermetically sealed casing into the lead retention assembly so as to couple the electronic circuits within the casing to lead-receiving receptacles within the lead retention assembly. Each lead has one or more electrical terminals on a proximal end thereof, typically in the form of a pin terminal and one or more conductive ring terminals. Typically, the pin is electrically coupled to a distal tip electrode and is therefore sometimes called the “tip terminal.” When the proximal end of the lead is inserted into the lead receptacle of a lead retention assembly, contacts within the receptacle come into contact with corresponding terminals on the lead so as to couple the lead to the electronic circuits within the implantable stimulation device via the feedthrough assembly. Needless to say, a completely dependable electrical connection is useful between the lead terminals and the corresponding lead retention assembly contacts. At the same time, the lead retention assembly being capable of releasing the lead from the lead receptacle during explantation or other subsequent surgical procedure may be useful, as may doing so while remaining tightly sealed against the entry of body fluids.
It is known in prior art lead retention assemblies to electrically and mechanically connect the proximal end of the lead within a receptacle of the lead retention assembly by a variety of expedients including captive fastening screw/collet arrangements and setscrews. In such prior art lead retention assemblies in which the lead is fixed within the lead receptacle using a setscrew, the setscrew is often threaded into an electrical connector block within the lead retention assembly. When the screw is advanced, it comes into contact with an associated terminal on the proximal end of the lead, mechanically and electrically coupling the lead and the lead retention assembly.
U.S. Pat. No. 6,984,145, issued Jan. 10, 2006, the entirety of which is incorporated herein by reference, discloses an example of a lead retention assembly mounted on an implantable cardiac stimulation device having a side-actuated mechanism for fixing and tightly sealing electrical leads inserted into lead receptacles.